Commotio Cordis: post Olympics reflections

October 6, 2016 Posted by Dr. Duncan Hogg no Comment

“Why do the Taekwondo players have protective gear and the boxers don’t?”, said my daughter watching the Olympics. One of those great “why?” questions that parents hope to answer with authority, but for which they often fall short of knowing the exact answer.

Let’s keep it heart-related I thought: “Well, if you hit someone perfectly in the chest you could kill them (probably not the best start!), so the padding on their chest might stop that… as well as reducing broken bones, bruising and the like”.

“They’re not trying to kill each other are they?”, came the next question. “No, they score points when they hit each other on the head and chest, so that’s what they do”. I seemed to have satisfied her curiosity for now, and was spared trying to give a tutorial on commotio cordis to a 9-year-old!

Prevalence

Of course, commotio cordis (CC) describes sudden cardiac death secondary to a chest wall impact, which leaves no evidence of cardiac trauma. It is extremely rare, but it is among the most frequent cardiovascular causes of sudden death in young athletes. Its victims are usually 9 to 16 years old boys, and the impact is with an energy routine for the sport.

Most contact sports have sadly caused cases, with the frequency appearing to be highest in baseball, softball and hockey (ice and field),  but also well reported in rugby, football, martial arts and cricket.

VF is the predominant rhythm found, and it’s said that successful resuscitation is difficult, with a resultant high mortality.

It does appear to be the case of perfect timing, with the mechano-electrical transduction of the impact inducing a ventricular arrhythmia.  The elegant study from 1998 using a pig animal model and projectiles triggered to impact at varying points on the surface ECG, showed that VF could be reproducibly induced by chest impacts during a 15msec time window on the up-slope of the T-wave. Link and co-workers further showed that the increasing density of the object directly correlated with the risk of inducing VF.

With the main culprit baseball, it was thought the incidence of CC would be highest in North America, but Maron and colleagues described it was comparable in other developed countries. Interestingly, there was a similar mix of projectile (60%) and bodily contacts causing events (40%); in competitive (60%) and recreational (15%) sport; a higher than expected number with footballs, recognising that they’re air-filled; and still a high mortality.

It’s clearly impossible to predict whether an impact will cause CC. So in the setting of youth sports, where their more compliant chest walls seem to be part of the vulnerability, how can the risks be minimised?

Disappointingly, the explanation to my daughter about the protective role of chest shields is probably not true, certainly as evidenced by testing in the pig model, and by many events still occurring despite them; but, developments to improve the efficacy of protection continue.

Why is the mortality rate so high?

VF in a normal heart isn’t usually difficult to abort, so why is the mortality rate so high? The key to the answer is seen in the later portion of the unsettling footage of the fatality of a 14-year-old during a karate bout. Clearly with the earlier appreciation of cardiac arrest and starting CPR, then access to, and use of an AED, the outcome from this event could, and most likely would, have been different.

Thankfully, there is clear evidence of progress here, with the survival post-CC much better now than over two decades ago- 10 vs 34%, and increasing to 58% in the last 5 years; almost certainly due to better awareness and earlier action.

Organising, delivering and maintaining support for any form of cardiac arrest event across all youth sporting settings will be extremely challenging, and costly; but its importance can’t be denied.

Very strong work continues in the UK from many charitable bodies, especially the BHF and Resuscitation Council (UK) , to help in all the ways needed to implement the chain of survival. But for public health, does central government not need to take the lead role in having a consistent and equitable level of support across the country, especially in schools?

Children will hopefully be inspired by the Olympics to participate in, and take up new sports. The potential for the highly unlikely occurrence of CC, even if more so in some sports, shouldn’t stop parents letting them do so. But, it is essential that administrators, sports leaders, parents, and other participants, have the knowledge, skills and support for action, if ever needed.

This Blog is Posted by Dr. Duncan Hogg

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